Electrical resistance-gdi l



(No Model.)

. J. NEBEL.

BLEGTRIOAL RESISTANCE 0011..

No. 581,170. Patented Apr. 20, 1897.

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UNITED STATES PATENT OFFICE.

JOHN NEBEL, OF LONDON, ENGLAND, ASSIGNOR TO THE SIEMENS & IIALSI'EELECTRIC COMPANY OF AMERICA, OF CHICAGO, ILLINOIS.

ELECTRICAL RESESTANCE=COIL SFECIFICATION forming part of Letters PatentN 0. 581,170, dated April 20, 1897'.

Application filed June 12, 1895. Serial No. 652,518. (No model.)Patented in England November 29, 1892, No. 21,782.

To aZZ whom it may concern.-

Be it known that I, JOHN NEBEL, a citizen of the German Empire, residingat 7% oodland Terrace, Old Charlton, London, in the county of Kent,England, have invented new and useful Improvements in ElectricalResistanceCoils, (Case No. 54,) of which the following is aspecification.

The subject-matter of this application has been patented in Englandunder date of N o vember 29, 1892, No. 21,782.

My invention relates to a rheostat or resistance-coil, and its object isto provide a form of rheostat that will be simple and strong inconstruction.

In accordance with my invention I provide a rheostat comprising a tubeof conducting material within which is placed the resistance-coil, aninsulating material, such as sand, being packed within the tube andabout the coil, the granular material serving to insulate the coil andto conduct the heat arising therefrom to the tube from whence it may bereadily radiated.

I will describe my invention by reference to the accompanying drawings,in which- Figure 1 is a view, partially in section, of the rheostatembodying my invention. Fig. 2 is a partial view of a modificationthereof. Fig. 3 is a partial sectional view of a further modification.

Like letters refer to like parts in the several figures.

The electrical conductor or resistancecoil a is supported within a tubeor casing b, which may be made of metal or other material adapted toconduct and radiate heat. The tubing is lined internally with a layer 0of insulating material, as enamel or asbestos, and plugs d d, ofinsulating material, are provided in the ends of the tube through whichthe conductor is adapted to pass, the plugs being made of slate, ceramicmaterial, or other suitable insulator. In Fig. 1 the tube is illustratedas provided upon its ends with screw-threads, upon which caps e e areadapted to be screwed to secure the plugs (Z d in position and to sealthe ends of the tube. In Fig. 2 a pin f is provided upon the tube, withwhich the bayonet-slotf, provided upon the cap c, is adapted to engage,whereby the cap is held in position. In Fig. 3 the tube is shown asprovided with internal threads with which the threads upon the cap 6 areadapted to engage, the cap being provided with a bore through which theplug cl is adapted to pass. IVithin the tube and surrounding the coil ais placed granular insulating material, which may be sand or any othergranular material possessing insulating properties and capable ofconducting heat. The heat generated by the passage of the currentthrough the coil is conducted through the granular material to the tubeZ), from the surface of which it is radiated.

It will be observed that the surface of the tube 1') is considerablygreater than the surface of the coil a, so that by this construction theradiating-surface of the rheostat is greatly increased.

Having described my invention, what I claim as new, and desire to securebyLetters Patent, is

1. The combination with the tube or casing of heat-conducting material,of a resistaucecoil supported therein, and insulating granular materialwithin said tube and surrounding said coil.

2. An electrical resistance-coil consisting of a wire helix of lowconductivity embedded in insulating granular material within a metaltube lined with insulating material and closed at the ends byinsulating-plu gs through which the wire passes, substantially asdescribed.

3. In a rheostat, the combination of aheatradiating casing, aresistance-wire within the casing, and loose sand packed within thecasing and separating the resistancewire from the casing, substantiallyas described.

4. In a rheostat, the combination with the coiled resistance\vii'e, of aheat-radiating casing therefor, means for sustaining the coil within thecasing, and a filler within the casing consisting of clear loose sandsurroundpacked within the case around theresistanceing' theresistance-coil, as described. wire. 10

5. In a rheostat, the combination of a tu- In testimony whereof I haveaffixed inysigbular heat-radiating case, sere\ eaps ciosing' nature inthe presence of two witnesses. 5 each end of the tubular case, aresistance- JOHN NEBEL.

Wire Within the case, insulating-bushing in Witnesses: each cap throughwhich connection is made GEO. P. SIMPSON,

with the resistance-wire, and loose sand THOMAS LAKE.

